Custom Indicator now working?

Issue:

I downloaded this Indicator Skeleton with one buffer and parameter.zip sample custom indicator just to try if I can make one someday, but it’s now showing anything on the chart.

Reproduce:
Download the file Indicator Skeleton with one buffer and parameter.zip
Compile it, npm install and npm run build

Upload the indicator and put it on the chart

Expected:

It should draw something in the chart?

Actual:

It doesn’t do anything. I think there’s an error sign just beside the indicator name on the indicator tile but there’s no error message that I can see.

I tried to upload the compiled js file but it’s not allowed so just rename it to .js

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